Have-a-go John Donnelly, 74, was just a step away from the safety of his secure entry close when the thug came at him from behind his back.

Quick-thinking John, known as Dan to his pals, said he shouted up to his ‘imaginary son’ to come down and help him confront the knifeman — which caused the would-be robber to run away.

He told the Telegraph: “I just wanted to give him a punch, to be honest.

“I gave him as good as I got verbally and basically told him where to go and asked him who he thought he was dealing with.

“I shouted up to my imaginary son ‘Johnny’ to come down and sort this guy out.” Dad of three daughters John had been socialising with friends in Greenock’s Broomhill Bar just minutes before the would-be thug pounced on him in Wemyss Bay Street, sometime between 10pm and 10.30pm on Tuesday night.

He said: “I actually had my key in the close door when he swore at me and demanded money.

“I think he was more surprised than anything when I turned round and gave him a mouthful back.” John, a retired Ravenscraig Hospital nurse, added: “He ran away and I just went up the stairs to my bed. I was a bit shaken by what happened, but I was determined he wasn’t getting anything from me.

“I went down to the police station the next day to report what happened.

“I hope he gets caught because I think he’ll do it again.

“He didn’t seem to be on drugs or anything because he was very clear in what he said. Maybe he wanted the money to go and buy drugs. He obviously thought I was an easy target for him.” Detectives are today hunting the masked hoodie-wearing knifeman.

The blade-brandishing thug is understood to have been loitering near flats and shops in nearby Broomhill Way when he started to follow OAP John.

Detective Inspector David Wagstaff, of Greenock CID, described the incident as ‘sickening’.

He told the Telegraph: “The victim was followed along Drumfrochar Road and assaulted at the front door of a close.

“The suspect presented a knife at him and demanded money.

“The victim started to shout for help which seems to have spooked the would-be robber, who ran away.” The wanted man is around 5ft 7in in height and of slim-build.

He was wearing a dark hooded top, with the hood up, and a dark scarf masking the lower part of his face.

John said: “All I could see was his eyes and the tip of what looked like a Stanley knife.” Police say that the would-be robber made off along Wemyss Bay Street towards Drumfrochar Road before possibly turning left.

The incident follows a similar one last week, when an elderly lady was mugged in Roxburgh Street.

DI Wagstaff said: “This is another attack on an elderly member of the community.

“It frankly sickens me that someone can plumb these depths.

“The victim was not hurt, but was shaken by what happened.

“It was obviously a frightening situation for him.” DI Wagstaff added: “I am appealing to anyone who saw the complainer being followed, or the attack itself, to get in touch with us immediately.

“People may have been in the area of the shops or the Broomhill Bar and seen something.” Anyone with information is asked to call the police on 101.